Fig. 4: Measurements of lamellipodium thickness and a proposed mechanism for cell migration. | Nature Communications

Fig. 4: Measurements of lamellipodium thickness and a proposed mechanism for cell migration.

From: Switch of cell migration modes orchestrated by changes of three-dimensional lamellipodium structure and intracellular diffusion

Fig. 4

a–c A schematic of the 3D SPT setup. The axial position of QD is determined by its diffraction ring radius from the off-focused channel (a). A thick lamellipodium has a larger fluctuation of diffraction ring radius of diffusing QDs (b, c). d Distributions of diffraction ring radius of QDs in fast and slow cells. e The measured lamellipodium thicknesses of fast (n = 15) and slow (n = 17) cells (p value = 2.1E−7). f Distributions of diffraction ring radius of QDs in the inside and outside of lamellipodium of a turning cell. g The measured lamellipodium thicknesses at the inside and outside parts of persistent (n = 10) and turning (n = 10) cells. Two-sample pair t-test; p = 0.32, the comparison of inside and outside for persistent cells; p = 0.0038, turning cells. h, i Typical AFM images of fast (h) and slow (i) moving cells. The inset images are the corresponding CMFDA images of the cells. The black boxes on the inset images indicate the region measured by AFM experiments. j Statistics of height in the front and the rear parts of lamellipodium (fast, n = 5; slow, n = 8). p = 0.35, 0.0011, 0.0076, 7.6E−5 for fast-rear and fast-front, fast-rear and slow-rear, fast-front and slow-front, slow-rear and slow-front, respectively. Inset: Height profile along the dashed line from the lamellipodium edges to the inside of the lamellipodium (along the arrow direction). k Proposed mechanism for dynamic switching of a keratocyte cell between the fast and the slow migration modes. The cell in each mode is presented in both top and side views, with the actin filaments inside the lamellipodium in orange. Black dots and lines with arrows represent the QDs and their trajectories. All statistical tests are two-sided. **P < 0.01; ***P < 0.001; NS not significant. All the boxes represent SD, where the center lines represent the medians, whiskers represent 1.5× outliers, and triangles represent the averages. Source data are provided as a Source Data file.

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